Though a member of the House of York, he switched sides to support the Lancastrians, before reverting to the Yorkists. He was later convicted of treason against his brother, Edward IV, and was executed (allegedly by being drowned in a butt of Malmsey wine). He appears as a character in William Shakespeare's plays Henry VI, Part 3 and Richard III, in which his death is attributed to the machinations of Richard.

Clarence had actively supported his elder brother's claim to the throne, but when his father-in-law (known as "the Kingmaker") deserted Edward IV to ally with Margaret of Anjou, consort of the deposed King Henry, Clarence supported him and was deprived of his office as Lord Lieutenant.[2] Clarence joined Warwick in France, taking his pregnant wife. She gave birth to their first child, a girl, on 16 April 1470, in a ship off Calais. The child died shortly afterwards. Henry VI rewarded Clarence by making him next in line to the throne after his own son, justifying the exclusion of Edward IV either by attainder for his treason against Henry VI or on the grounds of his alleged illegitimacy.[citation needed]

After a short time, Clarence realized that his loyalty to his father-in-law was misplaced: Warwick had his younger daughter, Anne Neville, Clarence's sister-in-law, marry Henry VI's son in December 1470. This demonstrated that his father-in-law was less interested in making him king than in serving his own interests and, since it now seemed unlikely that Warwick would replace Edward IV with Clarence, Clarence was secretly reconciled with Edward.[2]

Warwick's efforts to keep Henry VI on the throne ultimately failed and Warwick was killed in battle in 1471. The re-instated King Edward IV restored his brother Clarence to royal favour. As his father-in-law had died, Clarence became jure uxoris Earl of Warwick, but did not inherit the entire Warwick estate as his younger brother, Richard, Duke of Gloucester, had married (c. 1472) Anne Neville, who had been widowed in 1471. Edward intervened and eventually divided the estates between his brothers.[1] Clarence was created first Earl of Warwick on 25 March 1472.[3]

In 1475 Clarence's wife Isabel gave birth to a son, Edward, later Earl of Warwick. Isabel died on 22 December 1476, two months after giving birth to a short-lived son named Richard (6 October 1476 – 1 January 1477), and they are buried together at Tewkesbury Abbey in Gloucestershire. Their surviving children, Margaret and Edward, were cared for by their aunt, Anne Neville, until she died in 1485, when Edward was 10 years old.

Though most historians now believe Isabel's death was a result of either consumption or childbed fever, Clarence was convinced she had been poisoned by one of her ladies-in-waiting, Ankarette Twynyho, whom, as a consequence, he had judicially murdered in April 1477, by summarily arresting her and bullying a jury at Warwick into convicting her of murder by poisoning. She was hanged immediately after trial with John Thursby, a fellow defendant. Clarence's mental state, never stable, deteriorated from that point and led to his involvement in yet another rebellion against his brother Edward.

In 1477 Clarence was again a suitor for the hand of Mary, who had just become duchess of Burgundy. Edward objected to the match, and Clarence, left the court.[1]

The arrest and committal to the Tower of London of one of Clarence's retainers, an Oxford astronomer named Dr John Stacey, led to his confession under torture that he had "imagined and compassed" the death of the King, and used the black arts to accomplish this. He implicated one Thomas Burdett, and one Thomas Blake, a chaplain at Stacey's college (Merton College, Oxford). All three were tried for treason, convicted, and condemned to be drawn to Tyburn and hanged. Blake was saved at the eleventh hour by a plea for his life from James Goldwell, Bishop of Norwich, but the other two were put to death as ordered.

This was a clear warning to Clarence, which he chose to ignore. He appointed Dr John Goddard to burst into Parliament and regale the House with Burdett and Stacey's declarations of innocence that they had made before their deaths. Goddard was a very unwise choice, as he was an ex-Lancastrian who had expounded Henry VI's claim to the throne. Edward summoned Clarence to Windsor, severely upbraided him, accused him of treason, and ordered his immediate arrest and confinement.

Clarence was imprisoned in the Tower of London and put on trial for treason against his brother Edward IV. Clarence was not present – Edward himself prosecuted his brother, and demanded that Parliament pass a Bill of Attainder against his brother, declaring that he was guilty of "unnatural, loathly treasons" which were aggravated by the fact that Clarence was his brother, who, if anyone did, owed him loyalty and love. Following his conviction, he was "privately executed" at the Tower on 18 February 1478, by tradition in the Bowyer Tower, and soon after the event, the rumour gained ground that he had been drowned in a butt of Malmsey wine.[1]

Clarence is a principal character in two of William Shakespeare's history plays: Henry VI, Part 3 and The Tragedy of Richard III. Shakespeare portrays Clarence as weak-willed and changeable, his initial defection from Edward IV to Warwick is prompted by outrage at Edward IV's unwise marriage to Elizabeth Woodville. Despite several flowery speeches proclaiming loyalty to Warwick and to Henry VI, Clarence defects back to Edward IV's side almost as soon as he sees his brothers again; it takes only a few lines for his brothers to shame him into rejoining the Yorkist party. Several lines reference his penchant for wine.

In Richard III, the play opens with Gloucester having framed Clarence for treason, using a soothsayer to sow doubt in the King's mind about his brother, and in the first scene Clarence is arrested and taken to the Tower. Gloucester nimbly stage-manages Clarence's death, fast-tracking the order of execution and then intercepting Edward IV's pardon when he changes his mind. In Act One Scene Four, Clarence recounts a terrifying nightmare, in which he has been pushed (accidentally) into the ocean by Gloucester and drowns, then finds himself in hell, accused of perjury by the ghosts of Warwick and Prince Edward. When he is attacked by assassins sent by Gloucester, he pleads eloquently and nobly but is stabbed and drowned in a butt of wine. It is Clarence's death that sends Edward IV into a fatal attack of guilt. Clarence is the first character to die in the play and his ghost later appears to Gloucester, then already Richard III, and Henry Tudor, the future Henry VII of England, before the Battle of Bosworth Field, cursing his brother and encouraging Henry.